It’s the result of a shoulder injury that has nagged at Richardson throughout training camp.

Thursday, though, he says he’ll definitely be wearing Seahawks white when Seattle opens the preseason against the Broncos in Denver.

“I’m playing Thursday,” he said emphatically after practice. “I’m very excited to play in my first preseason game. It’s going to be like a World Championship for me. I can’t wait.”

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Mostly, the game marks Richardson’s debut in the NFL, and preseason or not, he said that’s a big deal.

It’s also, though, something of a homecoming for Richardson, who played at Colorado in nearby Boulder.

And it will also be a reminder of one of Richardson’s most memorable football moments just 11 months ago.

In the annual season-opening Colorado-Colorado State game played on the same turf, Sports Authority Field at Mile High, Richardson caught 10 passes for 208 yards and two touchdowns in what was his first game back after missing the 2012 season with an ACL tear.

It was those kinds of performances that compelled the Seahawks to pick Richardson with their first overall selection in the 2014 draft, the 45th overall.

And while the shoulder injury has led to some fits and starts, the Seahawks say Richardson has been as advertised when he has been on the field.

His football ability and speed, though, have never really been doubted.

What some draftniks wondered about were his size and durability.

Richardson insists the shoulder is nothing of concern, and that he intends to be full go in Seattle’s practice Tuesday.

“It’s just something that was bugging me and we finally worked out the kinks with it,’’ he said. “That’s all that was.”

His size, he said, is also coming around.

Richardson was listed at 170 pounds by Colorado last year. But he said more accurately it was in the 158-to-162 range.

Monday, he said he weighed 178.

“I feel really good at that size,” he said. “Stronger, still fast and able to make plays at this size. So I’m still 20 pounds heavier than I was when I came out.’’

Richardson said he can tell a difference on the field with a few more pounds.

“I’m more confident with having more weight,” he said. “But my biggest thing is to not be touched and to get down field and get in the open field, and I’m going to keep doing that.”

Still, recent shoulder issues aside, Richardson thinks he has proven in camp that he can hang in physically.

“Based on my size, a lot of people think that if they get their hands on me, that’s the end of the story,” he said. “But playing against the big guys that I go against every day — Richard (Sherman) and (Byron) Maxwell — I think that I will be just fine.”

Richardson said going against Seattle’s vaunted secondary has at times been “humbling.”

“But every rep is a learning experience for both sides, so it’s fun more than anything,” he said.

The biggest transition to the NFL, he said, has been mental.

“It’s just trying to think that I have to learn everything at one time instead of doing things gradually the way the coaches are trying to teach us,” he said. “Once I figured that out, it’s been smooth sailing.”

NOTES

• The Seahawks signed guard Wade Smith, an 11-year veteran who started the last four seasons for the Houston Texans, to add depth and competition on the offensive line. The move came a day after Michael Bowie, who had been waived as injured, was picked up by the Cleveland Browns. Smith was used at guard Monday but the Seahawks think he can help at any spot on the line.

Meanwhile, coach Pete Carroll explained that the team waived Bowie because it needed the roster spot now — since Bowie has less than four years of experience, he could not be assigned straight to the injured reserve list until Aug. 26. Carroll also confirmed the team’s unhappiness with Bowie’s condition, noting that “he came in 20 pounds overweight too, you know.”